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O: Fachverband Oberflächenphysik

O 21: Electronic Structure and Spin-Orbit Interaction I

O 21.2: Vortrag

Montag, 11. März 2013, 16:15–16:30, H42

Description of Rabi oscillations within time-dependent density functional theory — •Jeiran Jokar and Nicole Helbig — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Many physical processes stemming from the interaction of light with matter are non-linear in nature. A prototype of such a process is the Rabi oscillation, i.e. the oscillation between the ground state and an excited state when a monochromatic laser with a frequency close to the resonance is applied. It is one of the few analytically solvable cases of non-linear electron dynamics where the population of states changes dramatically in time. Due to the resulting change in the density the description of Rabi oscillations by density functional theory (DFT) suffers from shortcomings that can be traced back to the use of adiabatic approximations which leads to a time-dependent detuning of the resonant frequency. Here, we investigate Rabi oscillations in a one-dimensional model system containing two electrons in a triplet configuration using exact exchange (EXX) and the adiabatic local density approximation (ALDA) within time-dependent DFT. Contrary to the singlet case, where no resonant Rabi oscillations can be observed, we find that the EXX and ALDA calculations for the triplet state show a near-resonant behavior. A small detuning of the laser frequency even results in a resonant Rabi oscillation in the EXX case which hints at the detuning due to the approximate functional being constant in time. We discuss the differences between the singlet and the triplet excitations which lead to a time-dependent or constant detuning, respectively.